Cutting tooth for earth drilling and digging machines



July 1, 1969 V J. P. WATTS 3,453,658

CUTTING TOOTH FOR EARTH DRILLING AND DIGGING MACHINES Filed June 30, 1967 I H 3e 36 34a 36 y A 33 INVENTOR.

JAMES F. WATTS Q; 32

ATTORNEYS United States Patent 3,453,658 CUTTING TOOTH FOR EARTH DRILLING AND DIGGIN G MACHINES James P. Watts, 6930 E. Pinchot, Scottsdale, Ariz. 85251 Filed June 30, 1967, Ser. No. 650,378 Int. Cl. E2lb 9/35, 9/22; E21c 13/00 US. Cl. 175388 1 Claim ABSTRACT OF THE DISCLOSURE A cutting tooth for earth drilling and digging machines including a blade portion having a front cutting edge and a shank portion formed integrally with the blade and extending rearwardly therefrom. The rear edge of the blade is substantially thicker than the shank, forming a shoulder which extends generally perpendicularly down- This invention relates to earth drilling and digging apparatus.

More particularly, the invention concerns a novel cutting tooth for earth drilling and digging machines such as angers, trenchers, and the like.

In another aspect, the invention concerns a cutting tooth especially adapted for use in drilling and digging in hard earth, rock, or under other adverse drilling or digging conditions.

In still another respect, the invention concerns a novel cutting tooth adapted for use under adverse drilling conditions but which is interchangeable with standard drilling teeth used on conventional earth drilling angers which are designed and used primarily for drilling in soft ground, thereby adapting such conventional augers for use where severe drilling conditions are encountered.

Although the novel cutting teeth embodying the present invention will be hereafter described in the context of their use in earth drilling augers, persons skilled in the art will understand and appreciate that the cutting teeth can be likewise usefully employed in other types of earth drilling and digging apparatus, for example, in trenching machines, either of the wheel or ladder-type, and other such machines.

According to conventional practice, drilling contractors commonly employ different machines when different drilling conditions are encountered. Thus, when the drilling conditions are relatively good, i.e., soft ground, a conventional high production rate, earth drilling auger (commonly called a dirt auger) is employed. However, when adverse drilling conditions such as extremely hardpacked earth or rock are encountered, the drilling contractors typically use specially designed rigs of slower drilling speed and having specially designed cutting teeth which are not interchangeable with the cutting teeth used on the conventional dirt augers.

The use of differential types of drilling rigs, when different drilling conditions are encountered, slows down operations as it is frequently necessary to remove the dirt auger and its drilling machine from the vicinity of the hole being drilled when the auger has been advanced to refusal. Thereafter, the contractor then positions a special drill rig adapted for use under severe drilling conditions and its associated equipment and continues drilling at a lower speed.

It would be highly advantageous to provide a cutting tooth which is interchangeable with the conventional teeth ordinarily used on common dirt angers, but which is specially designed and adapted to permit the dirt auger to be used under the severe drilling conditions which normally require specially designed rigs. In this way, the down time due to changes in drilling conditions would be minimized as it would only be necessary for the operator to remove the auger from the hole, change the teeth, and continue drilling with the same rig.

Accordingly, it is an object of the present invention to provide a novel cutting tooth especially adapted for use under severe drilling conditions;

Another object of the invention is to provide such a tooth which is interchangeable with the teeth commonly used on conventional dirt augers;

Still another object of the invention is to provide a cutting tooth of the type described which will reduce down time due to changes in drilling conditions by making it unnecessary to use a specially designed, slowerspeed auger when extremely hard-packed earth or rock is encountered;

These and other, further and more specific objects and advantages of the invention will become apparent from the following detailed description of the invention taken in conjunction with the drawings, in which:

FIG. 1 is a perspective view of a cutting tooth embodying a preferred embodiment of the present invention;

FIG. 2 is a perspective view of the underside of the cutting tooth of FIG. 1;

FIG. 3 is a sectional view of the tooth of FIG. 1 taken along section line 3-3 of FIG. 4, and

FIG. 4 depicts a typical earth auger having the cutting teeth of FIGS. 1-3 mounted thereon.

The cutting tooth of the present invention is especially useful in conjunction with conventional earth drilling angers. Such angers generally include a central shaft, a pilot auger on the bottom end of the shaft, a cutter bar extending radially from the central shaft above the pilot auger, and a spiral screw flight aflixed to the central shaft and extending upwardly from the cutter bar.

In the vast majority of cases, the cutting teeth are affixed to the cutter bar by means of so-called friction pockets. These friction pockets generally comprise inverted channel members fixed to the cutter bar and forming pockets which frictionally engage the shank portions of cutter teeth to position the teeth in operative drilling position on the cutter bar.

In accordance with my invention, I have provided a novel cutting tooth which is interchangeable with the conventional cutting teeth of a dirt auger and which adapts the common dirt auger for use under severe drilling conditions such as extremely hard-packed earth or even in rocky formations.

The novel cutting tooth of the invention comprises a blade portion having a front cutting edge, side edges and a rear edge, and a shank portion formed integrally with and narrower than the blade portion. The shank portion extends rearwardly from the rear edge of the blade portion. The rear edge of the blade portion is substantially thicker than the shank portion and a shoulder is fonned at the juncture of the blade and shank portion. This shoulder depends substantially perpendicularly downwardly from the juncture of the blade and shank portions. When the shank of the tooth is frictionally engaged in the friction pocket on a cutter bar of a dirt anger, the shoulder depending downwardly from the blade bears against the cutter bar and substantially reduces the tendency of the cutting teeth to chatter during operation of the auger. This chatter results in flectional stresses which materially reduce the life of the cutting blade.

Referring now to the drawings, FIG. 1 is a perspective view of a cutting tooth which depicts the presently preferred embodiment of the invention. The cutting tooth comprises a blade portion generally indicated by reference character A and a shank portion generally indicated by reference character B. The blade portion has a front cutting edge 11, a rear cutting edge 12 and side edges 13 and 13a. The rear edge 12 of the blade portion A is substantially thicker than the shank portion B and forms a shoulder 14 which depends substantially perpendicularly downwardly from the juncture of the blade A and shank B portions of the cutting tooth. According to a preferred embodiment, the cutting tooth includes a carbide insert 15 in the blade which forms a cutting edge along the front edge 11 of the tooth.

FIG. 2 is a perspective view showing the underside of the tooth of FIG. 1. In another preferred embodiment, the cutting tooth is provided with one or more recesses 16 and 16a which provide passageways for rock chips, etc., dislodged by the cutting edge to pass to the rear of the blade as the blade advances without lifting the cutting edge and allowing the tooth to cut at its graduated rate. It will be understood, however, by those skilled in the art that the provision of such longitudinal depressions on the bottom surface of the tooth may be omitted Without rendering the tooth ineffective.

The mode of attachment of the tooth to the cutter bar of a typical dirt auger is illustrated in FIG. 4. The cutter bar 20 is affixed by means of welding or other suitable mode of attachment to the bottom end of the screw flight 21. The cutter bar carries a plurality of inverted channel members 23 which, with the cutter bar, form recesses 24 shaped to receive and frictionally engage the shank portion B of the cutter blade. The shoulder 14 formed at the juncture of the shank portion B and the blade portion A of the cutter blade bears against the forward edge 25 of the cutter bar 20 when the shank B is received in and frictionally engaged by the pocket 23. The bearing surface between the shoulder 14 and the leading edge 25 of the cutter blade materially strengthens the assembly and substantially reduces tooth chatter in the direction of the arrow C. In a preferred embodiment of the invention, as illustrated in FIGS. 1 and 2, the cutting edge of the tooth is disposed at an acute angle to the longitudinal axis D of the cutting tooth such that, when mounted on the cutter bar of an earth drilling or digging device, the cutting edge penetrates the earth or rock with a shearing, as distinguished from a crowding or breaking, action. In this way, I have found that it is possible to increase the drilling speed of augers and digging devices in which such teeth are employed by a factor of 20-10()% over such devices having standard cutting teeth. In one test, a standard 18- inch dirt anger with new teeth of the common design of the prior art Was drilled to refusal, the auger was removed from the hole and the teeth were replaced with the teeth embodying the present invention, the auger was replaced in the hole, and an acceptable drilling speed of 18 feet per hour was obtained in solid rock.

FIG. 4 illustrates the cutting teeth of the present invention secured in place in operative drilling position in an anger assembly. The auger assembly comprises a central shaft 31 having a pilot auger 32 aflixed to the lower end 33 of the shaft 31. Cutter bars 34 and 34a extend radially from the shaft 31 above the pilot auger 32. Friction pockets 35 receive the shank portions of the teeth 36. It will be noted that the angular displacement of the cutting edges of the teeth 36 enhances the shearing of the material being cut by the teeth 36 and reduces the crowding or breaking effect of the cutting edges of the teeth. This markedly increases drilling speed and reduces the rate of tooth wear.

Of course, as will be understood by those skilled in the art, in order to obtain the principal advantages of the present invention, it is necessary that any dirt auger or other digging machine be of sufiiciently rugged construction that it will have sufficient strength and mechanical integrity to take advantage of the ability of the teeth described above to drill in extremely hard ground or rock.

Various changes in the devices chosen for purposes of illustration in the drawings will readily occur to persons skilled in the art having regard for the disclosure hereof. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is not limited to the devices specifically illustrated in the drawings but, rather, only by a just interpretation of the following claim.

Having fully described the invention in such manner as to enable those skilled in the art to understand and practice the same, the invention claimed is:

1. A cutting tooth for an earth-drilling auger, which auger includes a central shaft,

a pilot auger on the bottom of said shaft,

a cutter bar extending radially from said shaft above said pilot auger,

a spiral screw flight aflixed to said shaft extending up wardly from said cutter bar, and friction pocket members comprising inverted channel members afiixed to said cutter bar, said friction pockets adapted to frictionally engage shank portions of cutting teeth to position said teeth in operative position on said cutter bar, said cutting tooth being interchangeably engageable in said friction pockets to specially adapt said earth-drilling auger to operate under severe conditions, said cutting tooth comprising:

(a) a trapezoidal-shaped blade portion having substantially parallel side edges, a rear edge substantially perpendicular to said side edges, and a front cutting edge which is inclined rearwardly at an acute angle with respect to said cutter bar when said tooth is affixed thereon in operative position, the face of said cutting edge being disposed substantially vertically when said tooth is in said operative position; and (b) a substantially flat shank portion formed integrally with said blade portion and extending rearwardly therefrom forming a continuation of the upper surface of said blade portion, said shank portion being substantially thinner than said blade portion, providing a shoulder depending downwardly from the juncture of said blade and shank portions, said shoulder positioned to bear against said cutter bar when said tooth is aflixed thereto in operative drilling position.

References Cited UNITED STATES PATENTS 1,997,887 4/1935 Prior 175394 X 2,701,126 2/1955 McClennan 175413 X 2,930,588 3/1960 Lord 175-394 X 3,318,401 5/1967 Carbert l-4l3 ERNEST R, PURSER, Primary Examiner.

U.S. Cl. X.R. --410, 413 

